Transformer cooling system



De@ 8. l 931. E. B. CLARKE 1,835,470

I TRANSFORMER COOLIG SYSTEM Filed Aug. 30, 1928 la. ,281l u I I6@ f@ INVENTOR Earl B. CIarKe l BY n I Z e i TToREY control.of forced-cooling systems Patented Dec. 8, 1931 UNITED sTA MANUFACTURING COMPANY, A

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ASSIGNOB T0 WSTINGHOUSE ELECTRIC &

CORPORATION 0F PENNSYLVAN anneau mea august so, 192s. serial No. 303,010.

to cooling automatic for a trans- My invention relates, generally, systems and particularly to the formers or other apparatus.

The application of radiators to oil-filled transformers as a means of dissipating heat generated inthe transformer is known, and, or the purpose of carrying out my invention, any suitable radiator construction may be utilized. It often occurs, in the operation of transformers, that the natural circulation of oil by gravity through the radiators is inadequate to dissipate enough heat to keep the transformer sufficiently cool for safe operation.

The heat dissipated by the coils of a transformer is a function of the load on the transformer. In an oil-cooled transformer of the radiator type this heat is conveyed, first to the oil and then through the walls of thel transformer tank and radiator to the surrounding medium, which is usually air or water.

It has been found desirable to operatel the coils of a transformer below a certain predetermined temperature. The greater the capacity ofthe cooling system for dissipating the heat generated by the transformer coils, the greater is the safe load that may be carried on a given transformer. 'The usual operating conditions of transformers are such that there is a considerable load variation during each twenty-four hours, so that the maximum capacity of the cooling system is only necessary during a part of this operating cycle.

My invention contemplates the use of circulating oil by gravity caused by changes in its temperature, and the additional use of a plurality of means that are responsive to the load on the transformer for increasing the capacity of thecooling system. In its broader aspect, my invention contemplates the use of a plurality of means for increasing the rate of circulation of the cooling oil or other fluid, or for bringing a cooling medium, such as air or water, into heat exchanging relation with the "oil, or both. The use of my system permits the operation of a given transformer, or other electrical apparatus, at much higher loadsthan would otherwise bepermissible for that size of equipment, and, at the same time, avoids the necessity of continuously operating the entire coolingsyste'm, orof depending upon the uncertainties of manual control of the cooling'syst'em. i

My invention provides for pumping oil through the radiators of the transformer ata higher'rate than it the action of gravity and, therefore, increases the heat-dissipating capacity of the radiators. Further coo ingl means are provided for forcing a' cooling medium, such as a draft* of air, about the outer surface of the radiators, thereby increasing the amount of heat 4transferred from the radiators to" the surrounding air. I

The object of my invention, generally stated, is to provide means for automatically varying'the rate ofy cooling of electrical apparatus. A more specific obj ect of my invention is to would naturallyI iow byv provide a plurality of yforced-cooling systems, each of which is controlled by thermally-responsive devices.

A further object of myinvention is to provide av plurality of forced-cooling systems, each of which is actuated at different prede'- termined temperatures of the body to be cooled.

Another object of my invention is to pro- C vide a cooling system for a transformer in f which the natural circulatiton of a heat-dissipating fluid is supplemented by a plurality of separate cooling systems, during predeter-f mined temperature ranges. y

Other objects of myinvention will become apparent to those skilled inthe art when the following description is considered in conjunction with the accompanying drawings, in which:

Figure 1 is a view, in sideelevation, of a transformer of conventional design which is equipped with cooling systems operated in accordance with my invention and having a section of its tank cut away to show the arrangement of elements; and

' Fig. 2 is a diagrammatic view of a system for automatically controlling the operation of the pumping motors of acooling system organized in accordance with my invention.

A transformer 10 comprising the usual core 7, coils 8 and tank 9 is provided with cooling radiators 11, in accordance with common ractice, one of which is show in Athe drawlngs, and oil 12, contained in the transformer 10, mayv circulatel from the tank 9through the radiator 11 to` be cooled ,by the airsu'rrounding it.'A

The radiator 11 comprises an upper header 13 and a lower-header '14 which are connected together aplurality of radiator tubes 15.

` The upper header 13 is connected to the tank 9 of the .transformer 10 near vthe top, and the lower vheader 14 isconnected to the transformer tank near the bottom. When the oi'l is` heated by the coils `8 of the transformer 10, it will ascend to the top of ,the transf former tank, since'its specific lgravity is decreased' by expansion and will flow into the upper header 13. As the oil 12 in the upper header 13 of the radiator 11 is cooled, its

specific gravity increases and it moves downv wardly and continues to cool so that a continuous circulation of oil occurs in and about the transformer core and coils and through the radiator 11.- Y

Such'a natural circulation ofoil is inadey 'quateto keep the transformer winding below its desired maximum temperature when.

the load on the transformer, and the heat dissipated by the transformer coils exceeds a j certain value.. Consequently, I' have provided 'an oil pump' 15 Whichis connected between the lowerheader 14 of the radiator 11 and the tank of the transformer 10. v

The pump 15 isprovided forcirculating the oil 12 through the radiator 11 at a higher rate than it would travel under its natural circulation by gravity. By this means, a

.greater rate of circulation of the oil .is eff fected, which results in conveying a greater amount of-heat from the transformer windings to the surrounding air.

An air'blower 16 has been provided to assist in cooling the oil by producing a con- I tinuous draft 'of air about the 'tubes 15 of theradiator 11, thus increasing the rate of heat transfer from the oil to the air. 4 It will be understood that the pump 16 may provide a circulation of fluids other than air about the radiator 11.

If the transformer 10 becomes so .loaded that the operation lof the oilvpumpA 15 is insuicient to keep the temperature of the oil -12 below a predetermined value, a motor driving the airblower will beautomatically The oil pumpl15' and the air pump 16 are operated by electric motors 15A and- 16A, respectively, .when theyarev connected to a sup 1y line 17 'Igxe transformer 10 is provided with a plu; ralityof thermometers or other thermallyresponsive devices-18 and 19 which indicate the temperature of the oil within the trans.- former at or near its upper surface, or that is in approximately the hottest portion of the oil contained by the transformer v10.

The thermometers 18 and 19 are provided,-

respectively, lwith contact members 20 and 21 so that an electrical circuit is completed by these" Contact members when the pointers of the thermometersl have reached a certain position, and will then indicatel that an abnormal temperature condition exists within the vtransformer 10. f

The contact members 20 of the thermometer 18, however, aredisposed' to become engaged at a temperature lower than that at which the contact members 21 of the thermometer 19 become engaged, so that as the temperature of the transformer continues to rise after the contact members 20 of the thermometer 18 have completed a circuit, the ther"-l mometer 19 will indicate 'suoli rise of temperature and, accordingly,

the contact members 21 will engage each other when the y indicator of the thermometer 19 has traveled to the predetermined position at which such contact members may complete another circuit.

The operations are controlled, respectively, by the thermometers 18 and 19 so that, when the pointers of the .respective thermometers have traveled to the right to'predetermined points, .the corresponding motors are set into operation.

When the temperature of the oil within the tank of the transformer 10 has reached the high temperature value at which the --contact members 20 of the thermometers 18 erimotor 15Aand by conductor 29, to the negatively energizedvconductor ofthe supply line 17. .The oil-pumping motor 15A is thereby started when the thermometer 18 has been moved to the' predetermined position at which its contact members 2() are engaged.

sof

of the motors 15A and 16A. l*

As hereinbefore set forth,the thermometer 19 has its contact members so disposed. that they do not become engaged unless the thermometer 19 indicates a higher temperature than that at which the contact members 20 of the thermometer 18 were engaged. Thus,

should -V the temperature of the transformer continue to rise after-the oiljpump 15v has i members of the relay 25, conductor 28, the

mal conditions of operation,

Vbeenv set-into operation,'the thermometer 19 will indicate such a rise in temperature and itsfpointer'will coi/ne to a position at which its contact members Will become engaged and energize a control circuit to start-the operation of the air-pump motor 16A, exactll as described above, for the starting of the oilpumping motor A.

VAlthough I'have provided a `system for forced-cooling a transformerunder abnorit will be apparent to those skilled in the art that my i A forced-cooling apparatus will not be normally operated since the thermometers 18 and 19 yWill be so designed that an unusual temperature condition mustA occur Within the transformer before either of the motors 15A and 16A will be connected to its source of supply or set into operation.

Thus, supply energy for the cooling of a transformer so equipped, but energy Will be automatically .supplied to the pumping devices upon the occurrence of an unusual or abnormal temperature condition Within the transformer. It is further pointed out that, if thc transformer 10 be operated under overload to produce theexcessive heating Within the oil 12 and set the pumps 15 and 16 in operation, the load on the transformer 10 may be decreased so thatsuch heating is no longer` existent, whereupon the thermometers 18 and 19 will recede and v"automatically interrupt the supply of energy to the pumping motors 15A and 16A, respectively, so that the transformer may continuuc to operate, being cooled by the natural circulation of oil by gravity Without the attention of an operator or attendant.l

Since it will possible to modify the embodiment set forth and adapt it to various ,applications Without departing from the spirit and scope of the invention, it is desired thatfthe foregoing description shallybe construed as merely-illustrative and not in aA limiting sense.

I claim as my invention: l. Ina cooling system, a plurality of motors and' `separate cooling means actuated tl1ereby,means responsive to. the temperature of the body to `be cooled for controlling the motors, said means being disposed to 'set one motor into operation upon fthe attain-1 ment. of a predetermined temperature and to set other Imotors into operation upon the attainment of a higher temperature.

' 2.. In a heat-generating apparatus, a coolcirculating fluids, a

lmg'system comprising plurality ofl pumps for forcing the circulationy ofthe fluids during the existence of certain-temperature conditions, means for operating one of said pumps when the apparatus reaches a predetermined temperature and means for', operating othery of said pumps upon a.. continued'rise in temperature to a it is not necessary to continuously lautomatic means for higher predetermined value during the operation of said first pump.

3. In an electrical apparatus susceptible to heating, in combination, a plurality of separate forced-Huid cooling means, thermallyresponsive mean's for controlling the cooling means when the apparatus reaches a predetermined temperature, said means being operated as the temperature of the apparatus continues to rise above said predetermined temperature. p

4. In a transformer-cooling `system comprising a transformer tank, a radiator, and a heat-conducting liquid normally circulated by gravity through the transforinertank and the radiator, a pump for forcing the circulation of the liquid, a pump for forcing the circulation of cooling gases -about the radiator, and means for operating thc pumps when the liquid in the transformer tank reaches a predetermined temperature.

5. In a transformer-cooling system comprising a transformer tank, a radiator, and a heat transferring. liquid normally circulated by gravity through the transformer tank and the radiator, a pump for forcing the circulation of the liquid under certain temperature conditions, a pump for forcing the circulation of gases about the radiator, automatic means for controlling the operation of lone pump when the liquid in the transformer 6.*In an oil-filled transformer tank having radiators through which oil normallycirculates by gravity, a pump for increasing the rate or circulation of oil through a radiator under certain conditions, means for impelling a draft of air about the radiator, and operating the pump and said means when the oil in the transformer tank attains a predetermined temperature.

7. In a cooling system for electrical apparatus, a fluid-circulating system for conveying heat from the apparatus Ato a cooling medium, means for forcing the flow of fluid through said circulatiing system, means for forcing a cooling medium into heat-exchanging relation with said Huid-circulating system, and means for automatically controlling the operation of said last two named meansy in accordance with an operating condition of said apparatus.

In a cooling system for velectrical apparatus,` a fluid-circulating system for con- .veying heat from the apparatus to a cooling August, 1928.

over different predetermined load ranges of said electrical apparatus. K

9. In a cooling system for -electrical apparatus,a'luid-circulating system for conveying heat from the apparatus to a cooling medium, means for forcing the flow of fluid through said circulating system, means for forcing a cooling medium into heat-exchanging relation with said fluid-circulating sys tem, automatic-means for causing the oper-Av ation of one oi said means over a predetermmed Worklngrange of sald apparatus, and automatic means for-causmg the operation of the other of said means over a dierentpredetermined Working range ratus.

I'n testimony whereof, I have hereunto subscribed my name this twenty-rst dayQ of EARL B. CLARKE.a

of said appa- 

